Greg, I don't think fact that you used your domain account instead of SPAdmin makes difference. Check this post: http://powerpivotgeek.com/server-installation/reported-problems/, specifically "Various errors after a previous uninstall fails when running NEW FARM install again". There is workaround for your reported error mesage IF you previously uninstalled SharePoint/SSAS integration and this is your second attempt to install. And just to clarify, when you create new user, option "change password on first login" should be unchecked.